A modified Curtius reaction: an efficient and simple method for direct isolation of free amine

The Curtius rearrangement and related reactions are often used to convert carboxylic acids to the corresponding primary amines. However, this reaction often requires harsh conditions for hydrolysis of the isocyanate intermediates to amines, and can also be contaminated by the formation of corresponding ureas due to the reactive nature of the intermediates. We have discovered that by quenching the isocyanate intermediates with sodium trimethylsilanolate, the free amines can be isolated after aqueous workup. This mild and fast procedure provides free amines in one pot with good yields.